/*
 * RMValidator.java    0.0.1   03/dic/2009
 *
 * Copyright (c) 2009 mentalsmash.org
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * The use of the Apache License does not indicate that this project is
 * affiliated with the Apache Software Foundation.
 */
package org.mentalsmash.tazio.transactions.management.wrm;

import org.mentalsmash.tazio.transactions.management.TazioTransaction;

/**
 * An object implementing the RMValidator role takes care of implementing the
 * protocol to remotely commit and validate a local pending transaciton
 * 
 * @version 0.0.1 03/dic/2009
 * @author Andrea Reale <andrea.reale@gmail.com>
 * 
 */
public interface RMValidator {
    /**
     * Calling this method takes care of contacting an available RM, and trying
     * to validate and commit globally the transaction passed as parameter.
     * <p>
     * The <tt>RMValidator</tt> will take care of implementing and performing
     * the complete protocol to globally commit a transaction.
     * <ol>
     * <li>It will call a commit() operation with at most once semantics on any
     * available RM</li>
     * <li>If the commit() call doesn't return a result, it will call a
     * whatAboutThisTransaction() operation on the group of RMs with at least
     * once semantics</li>
     * <li>If also the whatAboutThisTransaction() fails it gives up and returns
     * a rollback value</li>
     * </ol>
     * </p>
     * 
     * @param tx
     *            The transaction to send remotely
     * @return the committed sequence number of <code>tx</code> if succesfully
     *         committed. Otherwise a negative (hence invalid) sequenceNumber.
     */
    public long globallyValidateAndCommit(TazioTransaction tx);
}
